Kate Middleton releases beautiful new photo of Princess Charlotte to mark her sixth birthday

We still can't believe it ... but yesterday Princess Charlotte turned six!

In celebration of the young royal's sixth birthday, the Duke and Duchess of Cambridge released a new photo of their only daughter - and she is one beautiful young lady.

In the sweet snap, the little princess appears to be standing on a swing at the Cambridges' Norfolk residence, Anmer Hall.

According to the royal's official Instagram account, the photo - which was shot by Kate Middleton - was taken over the weekend.

Wearing a floral summer dress, the birthday girl is looking so grown up.

"Wishing Princess Charlotte a very happy sixth birthday today," the caption read alongside the photo on social media.

Happy birthday Princess Charlotte!